The present invention refers to laundry drying machine with vibrating fluff filter.
Nowadays the laundry drying machines usually comprise a casing comprising an outer casing and a loading/unloading door in which it is defined a drying air circuit adapted to cause heated drying air to circulate through a rotating drum in which the laundry can be loaded, so as to remove the moisture from the laundry.
In particular there are known condenser-type drying machines in which the drying air circuit is typically provided with an air-cooled condenser, i.e. an air/air heat exchanger, adapted to remove moisture from the hot moisture-laden drying air exiting the drum, and with an open-loop cooling air circuit adapted to circulate through the air-cooled condenser a stream of cooling air taken in from the outside ambient to cool the condenser, and to let out said stream of cooling air again into the outside ambient.
Through the drying air circuit, the hot and moisture-laden drying air is caused to leave the rotating drum and is conveyed towards the air-cooled condenser; then, the dehydrated drying air exiting the condenser is sent back into the drum, upon having been duly heated up again, so as to remove additional moisture from the clothes being tumbled in the drum.
Heating means are provided downstream from the air-cooled condenser to heat up the dehydrated drying air due to be sent again into the drum.
They are also known laundry drying machines in which the treatment process of the drying air is based on the utilization of a heat pump that is substantially constituted by a refrigerating circuit including a motor-driven compressor, a condenser, an expansion valve and an evaporator. The condenser and the evaporator of this refrigerating circuit are usually arranged in the drying air circuit, upstream of the rotating drum of the machine.
Further component parts, such as appropriate heating elements to heat up the working media (refrigerant medium and drying air), condensate wells or traps, and the like, may be provided to the purpose of improving the efficiency of the machine and keep the energy usage thereof as low as possible.
In the previously described laundry drying machines, the drying air circuit usually includes filtering and collecting means for removing the fluff (named also lint) from the drying air.
Such filtering means are required in order to prevent fluff, or lint, from being able to settle and build up on the heat-exchange surfaces of the air-cooled condenser, thereby affecting the performance and the efficiency thereof. In addition, these filtering means prevent fluff from dangerously piling up on the heating means, so as to ward off any fire risk.
The filtering means, however, have a major drawback in that they tend to most easily become clogged in the course of the drying operation, thereby involving substantial pressure losses in the drying circuit and hence, a corresponding increase in the power required to ensure a predetermined, satisfactory flow rate through the same drying circuit, along with a substantial variation in the flow rate in the course of the drying operation and a reduction in efficiency.
Another drawback derives from the fact that, for the laundry dryer machine to be able to perform at the highest possible performance level it is capable of ensuring, the need arises for the user, after each drying cycle is ended, to submit the filtering means to due maintenance and cleaning.
However, users tend to dislike such maintenance and cleaning chore, since this requires them to directly handle, i.e. come into contact, with fluff; furthermore, it is generally felt as representing itself a waste of time.
It should also be stressed that the full efficiency and performance capability of the tumble dryer come to depend on the kind of maintenance ensured by the user, actually. The consequences of a poor maintenance, or a maintenance that is not carried out as frequently as necessary, are therefore fully obvious.
However, fluff is anyway and unavoidably retained by the filtering means during a drying process and such fluff unavoidably builds up a resistance to the flow of the drying air therethrough, with the result that the flow rate of the operative process air is anyway reduced and the drying time needed to complete the ongoing drying cycle is increased accordingly.
An insufficient cleaning of these filters, and the consequent clogging of the same, can therefore cause the deterioration of the drying performances of the machine, and moreover a significant increase of the temperature of the air inside the drum, which can be dangerous.
In order to overcome such a problem, various solutions have been proposed; for example in EP1719833 is disclosed a clothes drying machine comprising a rotating drum, holding the clothes to be dried, an outlet mouth, from which the drying air is released after having flown through the drum, an exhaust conduit, into which flows the air issuing from the outlet mouth, a lint filter, formed substantially in the shape of a sector of a cylindrical surface, which is arranged in the exhaust conduit below the outlet mouth of the drum, with the axis thereof extending substantially parallel to the axis of rotation of the drum, a stationary wall, which is at least partially applied on to the outlet mouth and is provided with a plurality of perforations for the air leaving the drum and entering the exhaust conduit to pass therethrough.
There are provided automatic means adapted to ensure cleaning of the filter, or a part thereof, through a brushing, i.e. wiping action; this automatic means comprise a brush, connected to an end portion of a moving arm, which is hinged, on the other end portion thereof opposite to the brush, on to a rotation pin. The moving arm is slidably linked with a driving pin, which is adapted to rotate, by means of a respective rotation arm, about a driving spindle driven rotatably about its own axis by automatic driving devices.
This solution is therefore based on the fact that the lint filter is periodically automatically cleaned in a mechanical way, at time intervals which are controlled by the machine operation program.
This kind of mechanical cleaning of the filter, although effective, is hindered by a number of specific drawbacks, in particular the complexity of the mechanical cleaning device, and the fact that the filtering septum, being very thin, is also fairly delicate, and so a reiterated brushing can damage it, reducing or also eliminating the filtering action.
Furthermore sometimes the brushing of the filtering septum, instead of removing the lint from the latter, could cause the lint to get stuck into the filtering septum, in such a way to occlude it, consequently obliging the user to disassemble the filter for manually cleaning it, for example using compressed air or other suitable devices. It is also known DE 3438575 in which is disclosed an appliance for the drying of laundry which has a horizontally and rotably mounted drum for receiving the laundry to be dried; a hot-air stream is conveyed diagonally through this drum.
To mechanically remove the laundry lint from the hot-air stream, there is provided, in the circuit of the hot air, a vertically suspended filter bag, from which the lint is detached at intervals, with the hot-air flow cut off, by means of a vibrating device, and then falls into a lint-collecting chamber which can be closed in a controlled manner.
The vibrating devices takes the filter bag in vibration, so as to separate the lint from the walls of this filter, and make it fall into the lint-collecting chamber, from where it can be periodically removed. The vibrating devices can be both a pneumatic device and an electromechanical device, connected to the upper part of the filter bag by means of springs.
Anyway also this appliance is affected by an important drawback; in fact the user can remove the filter bag only by partially disassembling the drying machine, this operation being quite difficult and requiring specific tools and a lot of time to be done.
On the contrary the possibility to easily remove the filter is very important, particularly because, in case of fault of the vibrating device, the filter must be anyway cleaned manually to avoid the above mentioned problems due to its clogging.
The difficulty in the removal of the filter also makes it difficult to verify if the cleaning operation made by the vibrating device has been really effective, of if some fluff has remained attached to the filter, which could generate the above mentioned problems related to the clogging of the filter.
With this solution it is also difficult to replace the filter bag in case of need (for example if the filter bag is broken).
An electromechanical device for setting in vibration a filter is also illustrated in DE 3832730 in which it is disclosed a shaking device for a dust collector with a vertically oriented cylindrical air-permeable filter which is held by an upper cylindrical support closed by a cover. The support can be set in vibration by a vibrator having an armature, a magnetic coil and a stator; the armature of the vibrator is arranged on the cover and the stator together with the magnetic coil, and can vibrate freely relative to the armature-cover unit.
Also this solution is affected by the drawback that in case of fault of the vibrating device, the removal of the filter for the manual cleaning of the same is quite difficult and time consuming, and also requires the use of specific tools.